Posts
31
Joined
9/5/2017
Location
North Lima, OH
US
Okay... so I bought a yz250 today and ran like a raped ape and now won't even try to start. Has compression, and is getting gas but ran good earlier... so is it just a plug? I ran 32:1 as manual says but guy claims he ran it at 50:1. And oil coming out of head so instead of burning the oil it's blowing it out. So is my mixture the problem.
Most likely the reason it won't start is a fouled plug.
When the premix isn't burned it goes out the powervalve breather hose and drips onto the floor.
Try 40:1 or rejet.
The Shop
FWIW, I run my Y250 at 32:1 and use FMF's recommended jetting. Very close to stock just one size larger on the main.
Compensating for bad jetting by changing the gas ratio is apparently what the previous owner did. Theres no reason to run 50:1 on a yz250 unless you want it to blow up due to lack of lubrication.
Plenty of people run their 250 on less oil. I'm not one of them, but it's quite common with woods riders.
If you like the way the bike runs on 50:1, run your gas at 32:1 and jet for a leaner air fuel ratio to get the same effect. That way you get the lube and power.
When you get a 4 stroke remapped, they dont change the oil in the cylinder and crank. They adjust air/fuel ratio. Same principal for carb tuning.
IMO changing the fuel ratio is the lazy way out for trial and error testing to get good carb settings for your specific bike and track.
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